EP-A-0 274 322 describes a spraying installation for spraying a coating material onto articles to be coated, in which installation a multi-axis robot moves an atomizer for spraying coating material facing articles to be coated. In the example described below, the coating material is a primer, a paint, or a varnish, and the articles to be coated are motor vehicle bodies transported by a conveyor.
The atomizer is equipped with a reservoir containing the volume of paint that is necessary for performing the stage of spraying paint onto the vehicle body. After that stage, it is necessary to fill the reservoir again by coupling the atomizer to a preselected paint circuit, sometimes referred to as a “circulating” paint circuit. When filling the reservoir again, it is often necessary to change coating material, in particular so as to change the shade of color of the paint. It is therefore necessary to clean the reservoir and the channels of the atomizer, and the coupling zones, by rinsing them with a cleaning material such as a solvent.
That is why a prior art paint spraying installation generally includes at least two distinct coupling means placed respectively between the atomizer and the paint circuit and between the atomizer and the solvent circuit. Those coupling means comprise, amongst others, two distinct valves mounted on and/or in the atomizer for the purpose of controlling, respectively and successively, the flow of solvent and the flow of paint. During the cleaning stage, residual waste solvent and paint must also be collected and then conveyed to a treatment unit, which requires an additional valve. This also requires corresponding additional control members and components for actuating the various valves.
Unfortunately, said juxtaposed valves in the atomizer represent considerable overall size, regardless of their respective dimensions. That overall size increases the overall size of the atomizer and makes its structure more complex. In addition, that overall size reduces access to the other components of the atomizer during maintenance operations.
In addition, those three valves are interconnected via a network of common channels, in particular so as to make it possible to rinse the valve and the ducts for enabling paint to flow towards the reservoir. Unfortunately, the volume of those common channels is filled firstly with paint for the reservoir-filling and spraying stages and secondly with solvent for the cleaning stages, so that that volume gives rise to wastage of paint and to a relatively high consumption of solvent. Paint is also wasted when the reservoir is filled again without changing the shade of paint.
A particular object of the present invention is to remedy those drawbacks by proposing a valve that is compact, that significantly reduces the amount of paint wasted and the solvent consumption, and that simplifies the structure of the atomizer.